In the industrial field, a technique of transporting continuous flexible material such as paper, plastic film, metal foil (hereinafter called “web”), using rollers for supporting and transporting the web, which is called a web handling, is widely used. These days, the transport technique is applied to materials provided with the additional value such as liquid crystal color filter made by coating the liquid crystal on the plastic film. According to the increasing demand for such high value-added materials, the transport technique requires high speed, high efficiency and high precision.
Conventionally, various techniques of adjusting a web tension to stably transport the web are disclosed (see e.g. JP 2003-212406 A, JP 2000-143053 A).
For example, a dancer roller disposed between web transporting rollers is moved in the perpendicular direction to the transportation direction to adjust the tension applied to the web by using a pressing apparatus, thereby obtaining the stable transportation of the web without wrinkling and slipping.
However, considering the transporting speed becomes high, the conventional tension control may fail to remove damages such as wrinkles generated during transport. These problems are called web defects that are the technical objective in the industrial field to be solved.
It is thought that the wrinkles are caused by a misalignment, or a non-parallel arrangement of the web transporting rollers, which is adjusted by an operator with his experiences.
In the case that the operator uses the experiences to adjust the arrangement of the rollers, when the wrinkles are generated in the high value-added material such as the liquid crystal color filter, the material cannot be used, which causes a serious damage. In the case where the operator detects a sign of generating wrinkles by the experience during transporting the web and adjusts the arrangement of the rollers, the productivity depends on the operator's ability and the high-speed, high-efficiency transporting is not obtained.
The present invention solves the above-mentioned problems and aims to provide unexpected web transport apparatus, web transporting method and web transport control program capable of detecting the sign of wrinkling of the web during the web transport and of preventing the generation of wrinkles.